1. Field of the Invention
The present invention relates in general to passenger detection systems and methods, and relates in particular to an improved passenger detection system that places the airbag for the passenger, in the deployable or not-deployable state, depending on the seating conditions of the passenger sitting in the passenger seat in an automobile.
This application is based on Japanese Patent Applications Nos. Hei 10-061299, Hei 10-077870, Hei 10-077871, Hei 10-077872, Hei 10-077873, Hei 10-083797, Hei 10-083798, Hei 10-083799, Hei 10-097782, and Hei 10-153270, the contents of which are incorporated herein by reference.
2. Description of the Related Art
In general, an airbag apparatus in an automobile is aimed at protecting the driver of the vehicle from fatal injuries, in the event of a collision, and is now considered to be an essential item for automotive safety, and in recent years, an airbag is provided for the passenger as well as for the driver.
An example of such an airbag apparatus is shown in FIG. 96, and is comprised by: a driver-side squib circuit comprised by a series circuit including safety sensor SS1, squib SQ1, and a semiconductor switching device SW1 such as field effect transistor; a passenger-side squib circuit comprised by a series circuit including a safety sensor SS2, a squib SQ2, and a semiconductor switching device SW2 such as field effect transistor; an electronic accelerometer (impact sensor) GS; a control circuit CC for judging an impact force on the basis of output signals from the sensor GS, and to supply signals to the gate circuits of the switching devices SW1, SW2.
This air bag apparatus, when a collision occurs for whatever reason, safety sensor SS1, SS2 are closed responding to a relatively minor acceleration, and the squib circuits are placed in an operable state. And, when the control circuit CC judges that a collision has definitely taken place according to the signals from the accelerometer GS, signals are sent to the gates of switches SW1, SW2 and the switches SW1, SW2 are closed. As a result of a current flowing in the respective squib circuits, the driver-side and passenger-side airbags are deployed because of the heating in the squib SQ1, SQ2, and the occupants are protected from the collision impact.
However, this type of airbag apparatus is designed so that the airbags are deployed upon collision, regardless of the presence of a passenger so that, when an adult is sitting on the passenger seat, protective effect against collision can be expected, but when a child is sitting on the passenger seat, because the seated height is shorter and the head position is lower than an adult, the effect of airbag deployment on the child can be more damaging. Therefore, in some cases, it may be desirable that the airbag on the passenger-side be not deployed upon collision, when the passenger is a child.
Accordingly, in the past, an airbag apparatus such as the one shown in FIG. 97 has been proposed to address such a concern. This airbag apparatus includes a sensor SD to detect whether a passenger is seated, and the control circuit CC judges the seating condition according to the detected signal from the sensor SD, when a collision occurs, it is designed so that the control circuit CC makes the airbag apparatus deployable or not deployable. Proposed systems are based on: either to measure the weight of the passenger according to a weight sensor to decide if the passenger is an adult or a child; or to record an image of the passenger and decide between an adult or a child based on the processed image.
The weight method is capable of estimating substantially whether the passenger is an adult or a child, and based on the result, the airbag is placed either in the deployable state or not-deployable state, to safeguard the passenger in the event of a collision. However, body weight is subject to individual differences, and there is a serious concern in basing such a critical decision solely on loading factor, and the efficacy of such a system is in doubt.
The imaging method is able to reasonably estimate the seating condition of the passenger and decide whether the passenger is an adult or a child, but the method is based on comparing the current image data with various stored patterns so that the apparatus can be complex and expensive.
It is an object of the present invention to provide a passenger detection system and a method for precisely detecting the sitting conditions of a passenger occupying a seat, and based on the results of a detection process, an airbag apparatus is instructed to be in an appropriate operational state.
To achieve the objective, the present invention provides a passenger detection system comprising: a plurality of antenna electrodes disposed separately on a seat; an electric field generation device for generating a weak electric field around an antenna electrode; a switching circuit for selecting a particular antenna electrode from the plurality of antenna electrodes and connecting to the electric field generation device; an information detection circuit for generating a particular electric field around the particular antenna electrode, and obtaining information related to a current flowing in the particular antenna electrode resulting from applying the particular electric field; and a control circuit for receiving signal data from the information detection circuit and judging passenger seating conditions on the seat according to the signal data.
Aspect 2 of the present invention provides a passenger detection system having a plurality of antenna electrodes disposed separately on a seat; an electric field generation device for generating a weak electric field around an antenna electrode; a switching circuit for selecting a particular antenna electrode from the plurality of antenna electrodes and providing an electrical connection to the electric field generation device; an information detection circuit for generating a particular electric field around the particular antenna electrode, and obtaining information related to a current flowing in the particular antenna electrode resulting from applying the particular electric field; a control circuit for receiving signal data from the information detection circuit and judging passenger seating conditions on the seat according to the signal data; and an airbag apparatus for enabling to deploy, upon collision, an airbag designated for the seat; wherein the airbag apparatus is instructed by the control circuit to be either in the deployable state or not-deployable state according to judging data generated by the control circuit. Aspect 3 of the system is that the plurality of antenna electrodes are disposed on a sitting section and/or backrest section of the seat.
Aspect 4 of the present invention provides a passenger detection method based on disposing generating an electric field around a particular selected from a plurality of antenna electrodes; detecting information related to a current flowing in the particular antenna electrode resulting from applying the electric field; and judging passenger seating conditions according to signal data related to the information.
Aspect 5 of the present invention provides a passenger detection method comprising the steps of: disposing a plurality of antenna electrodes separately on a seat; selecting a particular antenna electrode from the plurality of antenna electrodes; generating an electric field on the particular antenna electrode; detecting information related to a current flowing in the particular antenna electrode resulting from applying the particular electric field; evaluating passenger seating conditions according to signal data related to the information and producing a judgment; sending the judgment to an airbag apparatus so as to place an airbag of the airbag apparatus either in the deployable state or not-deployable state.
As disclosed above, the present passenger detection system is based on a plurality of antenna electrodes disposed on a seat, and an electric field is generated by connecting the electric field generation device successively to each antenna electrode by means of a switching device. A current, resulting from the application of the electric field, flows in each antenna electrode depending on the passenger seating conditions. Therefore, by detecting information related to the current flowing in each antenna electrode, passenger seating conditions such as passenger loading and whether the passenger is an adult or a child can be detected readily.
Also, because high frequency low voltage signals are generated from one electric generation device and are distributed to the plurality of antenna electrode by the switching action of the switching device, circuit configuration is simple and the cost of the system is low.
Especially, the airbag in the airbag apparatus can be placed in a deployable or not-deployable state depending on whether the passenger is an adult or a child. For example, if a passenger is judged to be not an adult because of a low head height, the airbag is placed in the not-deployable state. Therefore, even if a collision occurs, the airbag is not deployed thus providing an appropriate action for a child passenger.
Aspect 6 of the present invention provides a passenger detection system comprising: a plurality of antenna electrodes disposed separately on a seat; an electric field generation device for generating a weak electric field around an antenna electrode; an amplitude control circuit for maintaining an amplitude of forward signals substantially constant; a switching circuit for selecting a particular antenna electrode from the plurality of antenna electrodes and providing an electrical connection to the electric field generation device; an information detection circuit for generating a particular electric field around the particular antenna electrode, and obtaining information related to a current flowing in the particular antenna electrode resulting from applying the particular electric field; and a control circuit for receiving signal data from the information detection circuit and judging passenger seating conditions on the seat according to the signal data.
Aspect 7 of the present invention provides a passenger detection system comprising: a plurality of antenna electrodes disposed separately on a seat; an electric field generation device for generating a weak electric field around an antenna electrode; an amplitude control circuit for maintaining an amplitude of forward signals substantially constant; a switching circuit for selecting a particular antenna electrode from the plurality of antenna electrodes and providing an electrical connection to the electric field generation device; an information detection circuit for generating a particular electric field around the particular antenna electrode, and obtaining information related to a current flowing in the particular antenna electrode resulting from applying the particular electric field; a control circuit for receiving signal data from the information detection circuit and judging passenger seating conditions on the seat according to the signal data; and an airbag apparatus for deploying, upon collision, an airbag designated for the seat; wherein the airbag apparatus is programmed by the control circuit to be either in the deployable state or not-deployable state according to judging data generated by the control circuit.
Aspect 8 of the present invention provides that the plurality of antenna electrodes are disposed on the sitting section and/or the backrest section. The invention presented in aspect 9 is a passenger detection system wherein the amplitude control circuit includes, at least, an amplitude varying circuit for varying a voltage amplitude of forward signals and an amplitude detection circuit for detecting the voltage amplitude and controlling the voltage varying circuit so as to maintain the voltage amplitude substantially constant, according to output signals from the amplitude detection circuit.
Aspect 10 of the present invention provides a passenger detection method by selecting a particular antenna electrode, and an electric field on the particular antenna electrode by impressing field signals, whose voltage amplitude is controlled substantially constant; detecting information related to a current flowing in the particular antenna electrode resulting from applying the particular electric field; and judging passenger seating conditions according to signal data related to the information.
Aspect 11 of the present invention provides a passenger detection method by selecting a particular antenna electrode, and an electric field on the particular antenna electrode by impressing field signals, whose voltage amplitude is controlled substantially constant; detecting information related to a current flowing in the particular antenna electrode resulting from applying the particular electric field; and judging passenger seating conditions according to signal data related to the information; and sending the judgment to an airbag apparatus so as to place an airbag of the airbag apparatus either in the deployable state or not-deployable state.
According to the invention presented in aspects 6 to 11, because the voltage amplitude of the forward signal from the selected antenna electrode is maintained substantially constant by the amplitude control circuit, little fluctuation occurs in the information related to the current detected by the information detection circuit so that stable data are obtained. Therefore, without compensating for the fluctuations in voltage amplitude, the stored data and the detected data can be compared readily, and the present detection method can offer high precision of detection of passenger seating conditions.
Also, seat has a plurality of separate antenna electrodes, and each antenna electrode is made to generate an electric field successively by the switching action of the switching circuit. Based on the electric field, a current flows successively in each antenna electrode according to the seating condition of the passenger. Therefore, by detecting information related to the current, passenger seating conditions can be determined accurately and readily.
Especially, the passenger airbag of the airbag apparatus is placed in either the deployable state or not-deployable state depending on whether the passenger is an adult or a child. For example, if a passenger is judged to be not an adult because of a low head height, the airbag is placed in the not-deployable state. Therefore, even if a collision occurs, the airbag is not deployed to as to produce a protective action appropriate for a child passenger.
Aspect 12 of the present invention provides a passenger detection system comprised by: a plurality of antenna electrodes disposed separately on a seat; an electric field generation device for generating a weak electric field around an antenna electrode; a switching circuit for selecting a particular antenna electrode from the plurality of antenna electrodes and providing an electrical connection to the electric field generation device; an information detection circuit for generating a particular electric field around the particular antenna electrode, and obtaining information related to a current flowing in the particular antenna electrode resulting from applying the particular electric field; and a control circuit for receiving signal data from the information detection circuit and judging passenger seating conditions on the seat according to the signal data; wherein control circuit includes: memory means for storing initial data SDn as reference data, obtained in a reference state including a vacant seat state by impressing an electric field on each antenna electrode and detecting a resulting current flow in each antenna electrode; reception means for receiving detected data ADn, obtained when starting the passenger detection system by impressing an electric field on each antenna electrode and detecting a resulting current flow in each antenna electrode; and judging means for computing a difference between the detected data ADn and the initial data SDn to produce essentially true data DTn, where DTn=SDnxe2x88x92ADn, and judging passenger seating conditions according to the essentially true data.
Aspect 13 of the present invention provides a passenger detection system comprising: a plurality of antenna electrodes disposed separately on a seat; an electric field generation device for generating a weak electric field around an antenna electrode; a switching circuit for selecting a particular antenna electrode from the plurality of antenna electrodes and providing an electrical connection to the electric field generation device; an information detection circuit for generating a particular electric field around the particular antenna electrode, and obtaining information related to a current flowing in the particular antenna electrode resulting from applying the particular electric field; a control circuit for receiving signal data from the information detection circuit and judging passenger seating conditions on the seat according to the signal data; an airbag apparatus having a capability to select an operational state of an airbag designated for the seat; and communication means for sending judgment data, based on a judgment derived by the control circuit, to the airbag apparatus; wherein control circuit includes: memory means for storing initial data SDn as reference data, obtained in a reference state including a vacant seat state by impressing an electric field on each antenna electrode and detecting a resulting current flow in each antenna electrode; reception means for receiving detected data ADn, obtained when starting the passenger detection system, by impressing an electric field on each antenna electrode and detecting a resulting current flow in each antenna electrode; and judging means for computing a difference between the detected data ADn and the initial data SDn to produce essentially true data DTn, where DTn=SDnxe2x88x92ADn, and judging passenger seating conditions according to the essentially true data.
Aspect 14 of the present invention provides a passenger detection method for a passenger detection system to detect seating conditions of a passenger seated on a seat by generating an electric field successively in a plurality of antenna electrodes disposed on the seat, detecting information related to a current flow in each antenna electrode caused by respective impressed electric field and judging passenger seating conditions according to the information, wherein the method includes the steps of: storing initial data SDn as reference data obtained in a reference state including a vacant seat state, produced by impressing an electric field on each antenna electrode and detecting a resulting current flow in each antenna electrode; receiving detected data ADn, obtained after starting the passenger detection system, by impressing an electric field on each antenna electrode and detecting a resulting current flow in each antenna electrode; computing a difference between the detected data ADn and the initial data SDn to produce essentially true data DTn, where DTn=SDnxe2x88x92ADn; and evaluating passenger seating conditions according to the essentially true data.
Aspect 15 of the present invention provides a passenger detection method for a passenger detection system to detect seating condition of a passenger seated on a seat by generating an electric field around each of a plurality of antenna electrodes disposed on the seat, detecting information related to a current flow in each antenna electrode caused by respective impressed electric field, judging seating conditions based on signal data related to the information, and sending the judgment to an airbag apparatus so as to place an airbag of the airbag apparatus either in the deployable state or not-deployable state, wherein the method includes the steps of: initializing sensors so as to store initial data SDn as reference data obtained in a reference state including a vacant seat state, produced by impressing an electric field on each antenna electrode and detecting a resulting current flow in each antenna electrode; and after starting the passenger detection system, receiving detected data ADn, produced by successively impressing an electric field on each antenna electrode and detecting a resulting current flow in each antenna electrode; computing a difference between the detected data ADn and the initial data SDn to produce essentially true data DTn, where DTn=SDnxe2x88x92ADn; evaluating passenger seating conditions according to the essentially true data; sending resulting evaluation data to airbag apparatus using communication means; and prior to placing the airbag apparatus in a selected operational state, performing an SRS process by exchanging evaluation data between a passenger detection circuitry and an airbag apparatus circuitry to examine whether or not there is abnormality in communication circuitry.
According to the invention presented in aspects 12 to 15, passenger evaluation is carried out by using the initial data SDn based on the reference state which is a vacant state of the passenger seat, and the detected signal data ADn is corrected so that the evaluation of the passenger seating conditions is carried out according to essentially true signal data DTn according to a relation DTn=SDnxe2x88x92ADn. Therefore, such initialization process can eliminate the effects of subtle variations in the installation condition of the antennae and the characteristics of the parts used, so that the passenger detection can be carried out reliably and precisely.
Also, signal data related to the current flowing in a selected antenna electrode resulting from the application of electric field are obtained from a difference of the initial value stored in the control stored circuit and the detected data, and judgment on the passenger seating conditions is made on the basis of the difference data, and the results are sent to the airbag apparatus through the communication device, and furthermore, these actions are repeated, so that the control of the airbag apparatus can be performed reliably and precisely according to the detected data of passenger seating conditions.
Especially, by arranging to communicate the passenger seating conditions between the control circuit and the control circuit of the airbag apparatus, problems in the can be identified and the system performance is improved.
Aspect 16 of the present invention provides a passenger detection system having a plurality of antenna electrodes disposed separately on a seat; an electric field generation device for generating a weak electric field around an antenna electrode; a switching circuit for selecting a particular antenna electrode from the plurality of antenna electrodes and providing an electrical connection to the electric field generation device; an information detection circuit for generating a particular electric field around the particular antenna electrode, and obtaining information related to a current flow resulting from the particular electric field; a control circuit for receiving signal data from the information detection circuit and judging passenger seating conditions on the seat according to the signal data; an airbag apparatus for enabling to deploy, upon collision, an airbag designated for the seat; and communication means for sending a resulting judgment to the airbag apparatus, wherein resulting evaluation data are sent to airbag apparatus using communication means; and prior to placing the airbag apparatus either in the deployable state or not-deployable state, checking system operation by exchanging evaluation data between a passenger detection circuitry and an airbag apparatus circuitry to examine whether or not there is abnormality in a communication circuitry between the passenger detection circuitry and the airbag apparatus circuitry.
Aspect 17 of the present invention provides a passenger detection method by: generating an electric field successively around a plurality of antenna electrodes disposed on a seat; detecting information related to a current flowing in successive antenna electrodes; receiving signal data regarding the information; evaluating passenger seating conditions according to received signal data and producing a judgment; sending the judgment to an airbag apparatus; and prior to placing an airbag of the airbag apparatus in a selected operational state; checking system operation by exchanging SRS data between a passenger detection circuitry and an airbag apparatus circuitry to examine whether or not there is abnormality in a communication circuitry between the passenger detection circuitry and the airbag apparatus circuitry.
Aspect 18 of the present invention provides a passenger detection method for a passenger detection system to detect passenger seating conditions on a seat by generating an electric field successively around a plurality of antenna electrodes disposed on a seat; detecting information related to a current flowing in successive antenna electrodes; judging passenger seating conditions according to signal data on the information; and sending a resulting judgment to an airbag apparatus so as to place an airbag designated for the seat either in the deployable state or not-deployable state, wherein when the seat is vacant, generating an electric field successively on the plurality of antenna electrodes; detecting information related to a current flowing in successive antenna electrode resulting from applying the electric field; initializing sensors so as to store initial data SDn obtained, in a reference state including a vacant seat state, by generating an electric field successively on a plurality of antenna electrodes and detecting information related to a current flow caused by respective electric field; and after starting the passenger detection system, receiving detected data ADn, produced by successively impressing an electric field on each antenna electrode and detecting a resulting current flow in each antenna electrode; computing a difference between the detected data ADn and the initial data SDn to produce essentially true data DTn, where DTn=SDnxe2x88x92ADn; evaluating passenger seating conditions according to the true data; sending resulting evaluation data to airbag apparatus using communication means; and prior to placing the airbag apparatus in a selected operational state, performing an SRS process by exchanging evaluation data between a passenger detection circuitry and an airbag apparatus circuitry to examine whether or not there is abnormality in a communication circuitry between the passenger detection circuitry and the airbag apparatus circuitry.
According to the invention presented in aspects 16 to 19, signal data related to the current flowing in an antenna electrode resulting from the electric field selectively generated on the plurality of antenna electrodes are received in the control circuit, and based on the signal data, passenger seating conditions are judged, and the judgment is sent to the airbag apparatus through the communication device, and these linked actions are performed repeatedly, therefore, the airbag apparatus can be controlled appropriately according to the passenger seating conditions.
Especially, the judgment of passenger seating conditions is exchanged between the control circuit and the airbag apparatus so as to check the communication circuit in this process, therefore, the airbag apparatus can be controlled appropriately and control reliability is increased.
Also, the passenger evaluation process is performed according to the initial data SDn stored in external memory which is used to correct the detected data ADn, so that the true data can be obtained from a relation DTn=SDnxe2x88x92ADn, and therefore, it is possible to eliminate such effects of subtle variations in the installation condition of the antenna electrode and the characteristics of the parts used, so that the passenger detection can be carried out reliably and precisely.
Aspect 20 of the present invention provides a passenger detection system comprised by an antenna electrode disposed on a seat and/or a vicinity of the seat, generation means for generating an electric field around the antenna electrode, detection means for detecting information related to a current flowing in the antenna electrode, and evaluation means for evaluating passenger seating conditions according to the information, wherein the antenna electrode is comprised by an antenna electrode section made of an electrically conductive material, and the antenna electrode section surrounds a planar space where there is no antenna electrode.
Aspect 21 of the present invention provides a passenger detection system comprised by an antenna electrode disposed on a seat and/or a vicinity of the seat, generation means for generating an electric field around the antenna electrode, detection means for detecting information related to a current flowing in the antenna electrode, evaluation means for evaluating passenger seating conditions according to the information, controlling means for selecting an operational state of an airbag apparatus according to the information, wherein the antenna electrode is comprised by an antenna electrode section made of an electrically conductive material, and the antenna electrode section surrounds a planar space where there is no antenna electrode.
Aspect 22 of the present invention provides an antenna electrode placed on a scat and/or a vicinity of the seat constructed so as to be used in a passenger detection system to generate an electric field around the antenna electrode, detect information related to a current flowing in the antenna electrode, and evaluate passenger seating conditions according to the information, wherein the antenna electrode is comprised by an antenna electrode section made of an electrically conductive material, and the antenna electrode section surrounds a planar space where there is no antenna electrode.
Aspect 23 of the present invention provides a antenna electrode placed on a seat and/or a vicinity of the seat constructed so as to be used in a passenger detection system to generate an electric field around the antenna electrode, detect information related to a current flowing in the antenna electrode, and evaluate passenger seating conditions according to the information, wherein the antenna electrode is comprised at least by an insulating base member and an antenna electrode section made of an electrically conductive material, and a lead wire having an electrical connection to the antenna electrode section, and the antenna electrode section surrounds a planar space where there is no antenna electrode.
Aspect 24 of the present invention provides an antenna electrode wherein the antenna electrode section is formed into a loop shape including spiral, or snake, comb, radiating shapes by using an electrically conductive metal wire or strip. The invention in aspect 25 is an antenna electrode, wherein the antenna electrode section is formed into a loop shape including spiral, or snake, comb, radiating shapes by using a process including screen printing, coating, spraying, vapor depositing or electroplating of an electrically conductive material. The invention in aspect 26 is an antenna electrode, wherein the antenna electrode section is formed into a loop shape including spiral, or snake, comb, radiating shapes by using an etching process of an electrically conductive material including metal strip or an electrically conductive material prepared by vapor deposition or electroplating.
Aspect 27 of the present invention provides an antenna electrode, wherein the base member is provided with a cover member for covering the antenna electrode section so as to unitize base member with the antenna electrode section and the cover member. The invention in aspect 28 is an antenna electrode, wherein the antenna electrode section is provided directly on parts constituting the seat, including seat outer covering and cushion member. The invention in aspect 29 is an antenna electrode, wherein the antenna electrode section and the lead wire are electrically connected by joining means including connection terminals and pressure terminals.
According to the invention presented in aspects 20 to 29, a plurality of antenna electrodes provided in the seat have a space bounded by the peripheries of the antenna electrode section where there is no conductive material of the antenna electrodes. Therefore, the wire material is reduced and the cost is lowered. Especially, when the antenna electrode section is made of an electrically conductive woven material, reduction in the material usage means lower cost.
Also, the antenna electrodes are provided with as many vacant spaces as possible without causing problems in use, so that the cushioning of seat is not affected. Therefore, seating comfort level is maintained and is comparable to those seats without the antenna electrodes. Particularly, when the space is in the center of the antenna electrode section, there is hardly any effect on the performance of the antenna electrodes.
Also, the overall antenna electrode section is produced by bonding a plurality of antenna electrodes on an insulating base member, so that it is possible to secure the spacing and arrangement of the antenna electrodes simply by positioning the base between the outer covering and the cushion material, without having to make any adjustments in their positions. After installing the section, there is no problem of shifting of the antenna electrodes. Therefore, information obtained from the perturbation current is reliable and the precision of passenger seating evaluation is improved.
Aspect 30 of the present invention provides a passenger detection system comprising: a plurality of antenna electrodes disposed separately on a sitting section and/or a backrest section of a seat; an electric field generation device for generating a weak electric field around an antenna electrode; a current detection circuit for applying the weak electric field to a particular antenna electrode and detecting a resulting current flowing in the particular antenna electrode; and a control circuit for evaluating passenger sitting conditions according to signal data received from the current detection circuit; wherein all antenna electrodes, excepting the particular antenna electrode selected for generating an electric field, are impressed with a direct current potential or earth potential.
Aspect 31 of the present invention provides a passenger detection system comprising: a plurality of antenna electrodes disposed separately on a sitting section and/or a backrest section of a seat; an electric field generation device for generating a weak electric field around an antenna electrode; a switching circuit having a plurality of switching devices for selecting a particular electrode and connecting the electric field generation device to the particular antenna electrode; a current detection circuit for applying the weak electric field to the particular antenna electrode and detecting a resulting current flowing in the particular antenna electrode; and a control circuit for evaluating passenger sitting conditions according to signal data received from the current detection circuit; wherein all antenna electrodes, excepting the particular antenna electrode selected for generating an electric field, are impressed with a direct current potential or earth potential.
Aspect 32 of the present invention provides a passenger detection system comprising: a plurality of antenna electrodes disposed separately on a sitting section and/or a backrest section of a seat; an electric field generation device for generating a weak electric field around an antenna electrode; a current detection circuit for applying the weak electric field to a particular antenna electrode and detecting a resulting current flowing in the particular antenna electrode; and a control circuit for evaluating passenger sitting conditions according to signal data received from the current detection circuit; wherein all antenna electrodes, excepting the particular antenna electrode selected for generating an electric field, are impressed with a direct current potential or earth potential, and evaluation data from the control circuit are sent to an airbag apparatus so as to place an airbag designated for the seat in the deployable state or not-deployable state.
Aspect 33 of the present invention provides a passenger detection method by generating a weak electric field selectively around a particular antenna electrode selected from a plurality of antenna electrodes disposed separately on a sitting section and/or backrest section of a seat; applying a direct current potential or earth potential to all antenna electrodes excepting the particular antenna electrode; and evaluating passenger seating conditions according to signal data of a perturbation current resulting from applying the weak electric field.
Aspect 34 of the present invention provides a passenger detection method by generating a weak electric field selectively around a particular antenna electrode selected from a plurality of antenna electrodes disposed separately on a sitting section and/or backrest section of a seat; applying a direct current potential or earth potential to all antenna electrodes excepting the particular antenna electrode; and evaluating passenger seating conditions according to signal data of a perturbation current resulting from applying the weak electric field to produce an evaluation result, and sending instruction data based on the evaluation result from the control circuit to an airbag apparatus so as to place an airbag designated for the seat in the deployable state or not-deployable state.
According to the invention presented in aspects 30 to 34, a plurality of antenna electrodes are disposed in the sitting section and/or the backrest section separately, and weak electric fields are generated successively around each electrode and the resulting signal data related to the perturbation current flowing in the antenna electrodes are processed to carry out the passenger detection process. However, one antenna electrode at a time is activated with ac signals while all other antenna electrodes are impressed with a dc voltage so that parasitic interference can be avoided. This approach is advantageous because of the stability of the electric field generated, and consequently, the perturbation current measurement is also stable. Therefore, by detecting the values of such perturbation current, it is possible to detect readily whether the seat is vacant or the passenger is an adult or a child, thereby improving the detection precision. Especially, the circuitry allows selection of setting the airbag apparatus to be either in the deployable state or not-deployable state so that unwanted airbag deployment can be prevented.
Especially, when a dc voltage from the electric power circuit is to be applied to all the antenna electrodes that are not generating an electric field, the same voltage can be shared with the oscillation circuit and control circuit, thus enabling to avoid having a separate power source for the dc voltage and the electric field generation process is stabilized at low cost.
Also, because a plurality of antenna electrodes can be selectively switched to the oscillation circuit and a dc voltage source by the switching action of the switching device by signals from the control circuit, contact to terminals a and b of the switching devices can be performed quickly and accurately. Thus, the perturbation current flowing in a particular antenna electrode can be detected precisely by the current detection circuit, and signal data regarding the perturbation current are received accurately in the control circuit.
Aspect 35 of the present invention provides a passenger detection system comprising: a plurality of antenna electrodes disposed separately on a seat; an electric field generation device for generating a weak electric field around an antenna electrode; a switching circuit for selecting a particular electrode and connecting the electric field generation device to the particular antenna electrode; an information detection circuit for applying the weak electric field to the particular antenna electrode and detecting information related to a current flowing in the particular antenna electrode resulting from applying the weak electric field; and a control circuit for evaluating passenger sitting conditions according to signal data received from the information detection circuit; wherein the electric field generation device outputs high frequency low voltage signals having a rectangular waveform.
Aspect 36 of the present invention provides a passenger detection system comprising: a plurality of antenna electrodes disposed separately on a seat; an electric field generation device for generating a weak electric field around an antenna electrode by outputting high frequency low voltage signals having a rectangular waveform; a switching circuit for selecting a particular electrode and connecting the electric field generation device to the particular antenna electrode; an information detection circuit for applying the weak electric field to the particular antenna electrode and detecting information related to a current flowing in the particular antenna electrode resulting from applying the weak electric field; and a control circuit for evaluating passenger sitting conditions according to signal data received from the information detection circuit to produce an evaluation result, and sending instruction data based on the evaluation result from the control circuit to an airbag apparatus so as to place an airbag designated for the seat in the deployable state or not-deployable state.
Aspect 37 of the present invention provides a passenger detection system, wherein a plurality of antenna electrodes are disposed on a sitting section and/or a backrest section of a seat. The invention in aspect 38 is passenger detection system, wherein electric field generation device generates high frequency low voltage signals of a rectangular waveform by switching a direct current voltage maintained at a positive constant voltage at a selected frequency. The invention in aspect 39 is a passenger detection system, wherein electric field generation device generates high frequency low voltage signals of a rectangular waveform by dividing a clock signal in a control circuit at a selected interval.
Aspect 40 of the present invention provides a passenger detection method by generating a weak electric field selectively around a particular antenna electrode selected from a plurality of antenna electrodes disposed separately on a seat; applying high frequency low voltage signals of a rectangular waveform on the particular antenna electrode; and detecting information related to perturbation current flowing is the particular antenna electrode; and evaluating passenger seating conditions according to signal data related to the information.
Aspect 41 of the present invention provides a passenger detection method by generating a weak electric field selectively around a particular antenna electrode selected from a plurality of antenna electrodes disposed separately on a seat; applying high frequency low voltage signals of a rectangular waveform on the particular antenna electrode; and detecting information related to a perturbation current flowing is the particular antenna electrode; and evaluating passenger seating conditions according to signal data related to the information to produce an evaluation result, and sending instruction data based on the evaluation result from the control circuit to an airbag apparatus so as to place an airbag designated for the seat in the deployable state or not-deployable state.
According to the invention presented in aspects 35 to 41, the antenna electrodes disposed on the seat are impressed with high frequency low voltage (HFLV) signals of a square waveform by the electric generation device, therefore, the circuit is simplified by adopting the method of switching a direct voltage source. Therefore, not only the electric field generation circuit but other component circuits are also simplified, so that the system cost is lowered.
Especially, electric field generation device may include an HFLV source to produce substantially rectangular waveform by switching of a positive electrical power source based on clock signals in the control circuit, or by dividing the clock signal in the control circuit. This further simplifies the control unit circuit, and system cost is further lowered.
Further, forward signals sent to the antenna electrodes are substantially at a constant voltage of a square waveform, therefore, data related to information obtained by the information detection circuit can be processed by a simple circuit, and the passenger seating conditions can be determined even more reliably and precisely.
Aspect 42 of the present invention provides a passenger detection system comprising: an antenna electrode disposed on a sitting section and/or a backrest section of a seat; an electric field generation device for generating a weak electric field around the antenna electrode; an ac-dc conversion circuit for converting an alternating current line voltage in a forward line, related to a perturbation current flowing in the antenna electrode resulting from the weak electric field generated around the antenna electrode produced by connecting the antenna electrode to the electric field generation device, to a direct current voltage; and a control circuit for judging passenger seating conditions according to evaluation data output from the conversion circuit.
Aspect 43 of the present invention provides a passenger detection system comprising: a plurality of antenna electrodes disposed separately on a sitting section and/or a backrest section of a seat; an electric field generation device for generating a weak electric field around an antenna electrode; a switching circuit for selecting a particular electrode and connecting the electric field generation device to the particular antenna electrode; an ac-dc conversion circuit for applying the weak electric field to the particular antenna electrode, and converting a resulting alternating current line voltage in a forward line related to a perturbation current flowing in the particular electrode to a direct current voltage; and a control circuit for judging passenger seating conditions according to signal data output from the conversion circuit.
Aspect 44 of the present invention provides a passenger detection system comprising: a plurality of antenna electrodes disposed separately on a sitting section and/or a backrest section of a seat; an electric field generation device for generating a weak electric field around an antenna electrode; a switching circuit for selecting a particular electrode to serve as a sending electrode and selecting a pairing electrode serving a receiving electrode, and connecting the electric field generation device to the particular antenna electrode; an ac-dc conversion circuit for generating a weak electric field between a resulting pair of antenna electrodes, and converting a resulting alternating current line voltage in a forward line related to a perturbation current flowing in the particular electrode to a direct current voltage; and a control circuit for judging passenger seating conditions according to signal data output from the conversion circuit.
Aspect 45 of the present invention provides a passenger detection system comprising: a plurality of antenna electrodes disposed separately on a sitting section and/or a backrest section of a seat; an electric field generation device for generating a weak electric field around an antenna electrode; a switching circuit for selecting a particular electrode and connecting the electric field generation device to the particular antenna electrode; an ac-dc conversion circuit for applying the weak electric field to the particular antenna electrode, and converting a resulting alternating current line voltage in a forward line related to a perturbation current flowing in the particular electrode to a direct current voltage; and a control circuit for judging passenger seating conditions according to signal data output from the conversion circuit to produce an evaluation result, and sending instruction data based on the evaluation result from the control circuit to an airbag apparatus so as to place an airbag designated for the seat in the deployable state or not-deployable state.
Aspect 46 of the present invention provides a passenger detection system comprising: a plurality of antenna electrodes disposed separately on a sitting section and/or a backrest section of a seat; an electric field generation device for generating a weak electric field around an antenna electrode; a switching circuit for selecting a particular electrode and connecting the electric field generation device to the particular antenna electrode; an ac-dc conversion circuit for applying the weak electric field to the particular antenna electrode, and converting a resulting alternating current line voltage in a forward line related to a perturbation current flowing in the particular electrode to a direct current voltage; and a control circuit for judging passenger seating conditions according to signal data output from the conversion circuit.
Aspect 47 of the present invention provides a passenger detection system comprising: a plurality of antenna electrodes disposed separately on a sitting section and/or a backrest section of a seat; an electric field generation device for generating a weak electric field around an antenna electrode; a switching circuit for selecting a particular electrode and connecting the electric field generation device to the particular antenna electrode; an ac-dc conversion circuit for applying the weak electric field to the particular antenna electrode, and converting a resulting alternating current line voltage in a forward line related to a perturbation current flowing in the particular electrode to a direct current voltage; and a control circuit for judging passenger seating conditions according to signal data output from the conversion circuit to produce an evaluation result, and sending instruction data based on the evaluation result from the control circuit to an airbag apparatus so as to place an airbag designated for the seat in the deployable state or not-deployable state.
Aspect 48 of the present invention provides a passenger detection system, wherein an RC time constant circuit is formed by capacitance components existing in a vicinity of an antenna electrode and a resistor connected in series to a forward circuitry including an electric field generation device. The invention in aspect 49 is a passenger detection system, wherein an impedance conversion circuit is provided between a forward circuitry for sending output signals from an electric field generation device and an ac-dc conversion device. The invention in aspect 50 is a passenger detection system, wherein the impedance conversion circuit is comprised by an operational amplifier having an amplification factor of 1. The invention in aspect 51 is a passenger detection system, wherein the control circuit is comprised, at least, by memory means for storing threshold value related to passenger seating conditions, means for receiving output signals from an ac-dc conversion circuit, and a judging section for judging passenger seating conditions by comparing threshold values with received signal data.
Aspect 52 of the present invention provides a passenger detection system, wherein the electric field generation device, the ac-dc conversion circuit, and the control circuit are housed in a common housing to form a control unit, which is incorporated in the seat. The invention in aspect 53 is a passenger detection system, wherein the electric field generation device, ac-dc conversion circuit, and the control circuit are housed in a common housing to form a control unit, and those constituting elements requiring an electric power source are supplied with power from an electric power source Vcc outputting a constant direct current voltage.
According to the invention presented in aspects 42 to 53, a current related to the stray capacitance components existing around the seat flows in the antenna electrodes, and in such a case, the waveform of the forward signals from the electric generation device is dependent on a RC time constant of the circuitry, and the rise time of the signals is affected and the resulting rounding effect of the rise time depends on whether the passenger is an adult or a child. The resulting ac voltage can be converted in the ac-dc conversion circuit to obtain distinguishable dc signals. This signal data are received in the control circuit and based on the signal data related to the dc current, passenger seating conditions can be determined precisely.
Also, because of the presence of the impedance conversion circuit between the signal line and the ac-dc conversion circuit, the input-side has a high impedance and the output-side has a low impedance. Therefore, when the control circuit receives dc output signals from the ac-dc conversion circuit, current drain by the control circuit does not affect the performance of the signal line. Therefore, passenger seating conditions can be detected with high precision.
Also, the electric power circuit as an element in the control unit produces a singular power source Vcc by reducing the voltage form the battery power to a singular dc voltage so that all the elements in the control unit requiring the electrical power can be served by the same constant voltage Vcc, therefore, the electric power circuit and the structure of the control unit can be simplified, so that the overall unit is simplified and the system cost is lowered.
Because the control unit is housed within the same housing as other components such as the electric field generation device, switching circuit, impedance conversion circuit, ac-dc conversion circuit; control circuit; power circuit, so that assembly into the seat is facilitated. Especially, an installation space is readily available near the seat frame or its vicinity, therefore, even if the size of the control unit becomes slightly larger, it can be simply and readily accommodated near the frame.
Also, the passenger seating condition is judged from the output dc signals from the ac-dc conversion circuit and analyzed by the control circuit in terms of a plurality of antenna electrodes, which are selected by the switching circuit. Therefore, the control circuit bases its decision on a large amount of perturbation data obtained from different antenna electrodes, thereby improving the detection capability and reliability of the passenger detection system even more.
Aspect 54 of the present invention provides a passenger detection system comprising: an antenna electrode disposed on a sitting section and/or a backrest section of a seat; an electric field generation device for generating a weak electric field around the antenna electrode; an antennae interface circuit including a detection circuit for detecting information related to a perturbation current flowing in the antenna electrode resulting from applying a power from the electric field generation device; a correction interface circuit including a detection circuit for detecting information related to a perturbation current flowing in the antenna electrode resulting from applying a power from the electric field generation device; and a control circuit for correcting signals output from the antennae interface circuit according to signal data output from the antennae interface circuit and the correction interface circuit; wherein the antennae interface circuit and the correction interface circuit are configured similarly and the antennae interface circuit is connected to an antenna electrode and the correction interface circuit is not connected to an antenna electrode and is open-circuited.
Aspect 55 of the present invention provides a passenger detection system comprising: an antenna electrode disposed on a sitting section and/or a backrest section of a seat; an electric field generation device for generating a weak electric field around an antenna electrode; an antennae interface circuit including a detection circuit for detecting information related to a perturbation current flowing in an antenna electrode resulting from applying a power from the electric field generation device; a correction interface circuit including a detection circuit for detecting information related to a perturbation current flowing in an antenna electrode resulting from applying a power from the electric field generation device; a control circuit for correcting signals output from the antennae interface circuit according to signal data output from the antennae interface circuit and the correction interface circuit; and an airbag apparatus that can be placed in a specific operational state according to judgment data generated by the control circuit; wherein the antennae interface circuit and the correction interface circuit are configured similarly and the antennae interface circuit is connected to an antenna electrode and the correction interface circuit is not connected to an antenna electrode and is open-circuited.
Aspect 56 of the present invention provides a passenger detection system, wherein the antennae interface circuit is comprised of, at least: an electric field generation device for generating a weak electric field around an antenna electrode; an ac-dc conversion circuit for connecting an antenna electrode to the electric field generation device to generate an electric field, and converting ac voltage related to a perturbation current flowing in the antenna electrode, resulting from applying the electric field, to dc data. The invention in aspect 57 is passenger detection system, wherein an RC time constant circuit is formed by capacitance components existing in a vicinity of an antenna electrode and a resistor connected in series to a forward circuitry including an electric field generation device. The invention in aspect 58 is passenger detection system, wherein an impedance conversion circuit is provided between a forward circuitry for sending output signals from an electric field generation device and an ac-dc conversion device. The invention in aspect 59 is passenger detection system, wherein the impedance conversion circuit is comprised by an operational amplifier having an amplification factor of 1.
Aspect 60 of the present invention provides a passenger detection system, wherein the control circuit is comprised of, at least: memory means for storing signal data output from the correction interface circuit; means for receiving signals output from the antennae interface circuit; a correction section for compensating for drift according to correction data received; an evaluation section for evaluating passenger seating conditions according to correction results output from the correction section. The invention in aspect 61 is a passenger detection system according to one of aspect 54 or 55, wherein the antennae interface circuit and the correction interface circuit are comprised by, at least: an electric field generation device; a current detection device for detecting a perturbation current produced by application of power by the electric field generation device; wherein the antennae interface circuit is connected to an electrode and the correction circuit is not connected to an antenna electrode and is open-circuited.
According to the invention presented in aspects 54 to 61, the antennae interface circuit and the correction interface circuit have essentially the same configuration of circuit components, and the electric generation device in the antennae interface circuit is connected to an electrode while the electric generation device in the correction circuit is not connected to an antenna electrode and is open-circuited. Therefore, output signals Sin, Hin from the respective interface circuits are affected by the same level of drift, so that by calculating the difference portion D1 between the output signals Sin, Hin, the drift components in each interface circuit can be eliminated.
In addition, by calculating the output signals Sin, Hin and the difference portion D1, essentially true signal data D2 can be obtained according to a relation D2=(Hinxe2x88x92(Sin+D1)). Therefore, even is the output signals from the antennae interface circuit are affected over time by thermal effects, passenger seating conditions can always be determined according to correct information data. For example, the system enables to avoid misdiagnose passenger seating conditions such that even though an adult is seated, erroneous judgment indicates that a child is seated.
Further, the control circuit makes judgment based on essentially true signal data D2 so that the airbag apparatus can be controlled according to correct passenger seating conditions.
Aspect 62 of the present invention provides a passenger detection system comprised by antenna electrodes disposed on a seat inside an automobile connected, using a shielding cable whose signal line is shielded by a shielding line, to a signal processing circuit for detecting passenger seating conditions by processing signal data related to a perturbation current flowing in an antenna electrode resulting from applying an electric field generated about the antenna electrode, wherein a buffer circuit, for maintaining signal levels of signal line and shield line at a same level, is connected between the signal line and the shield line.
Aspect 63 of the present invention provides a passenger detection system, wherein a plurality of antenna electrodes are disposed on the seat, and antenna electrodes and the signal processing circuit are wired using a plurality of shielding cables.
Aspect 64 of the present invention provides a passenger detection system, wherein a common buffer circuit is connected to each of the plurality of antenna electrodes and signal processing circuit through a respective switching element.
In this case, the signal line in the shield cable and the buffer circuit connected to the shield line are connected to an operational amplifier to maintain the same potential in the signal line and the shield line. This buffer circuit the signal levels in the corn circuit are maintained at the same potential level so that the RC time constant between the signal and shield lines does not affect the signal communication between the control circuits and the signal error in evaluating the passenger seating conditions can be eliminated.
The buffer circuit can resolve the problems of scatter in the signal levels resulting from the differences in the lengths of the shield cables, therefore, design freedom is increased by not having to limit the cable length.
Also, by using a common buffer circuit for a plurality of shield cables, cost is reduced, and in particular, circuit configuration can be simplified significantly for a passenger detection system based on many antenna electrodes.